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Formula for the Calculation of PPM (Parts Per Million)

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Post Number #1
5th September 2007, 02:42 PM
 Mumus Total Posts: 57
Formula for the Calculation of PPM (Parts Per Million)

Hi All,

Can someone help with a formula for calculation of PPM (parts per million) ?

Thanks.

Post Number #2
5th September 2007, 02:59 PM
 Stijloor Total Posts: 15,191
Re: Calculation of PPM

Quote:
 In Reply to Parent Post by Mumus Hi All, Can someone help with a formula for calculation of PPM (parts per million) ? Thanks.
Would this help?

http://www.engin.umich.edu/class/eng...s/ppm_tabl.htm

Search The Cove! Good stuff will pop up.
 Thanks to Stijloor for your informative Post and/or Attachment!
Post Number #3
5th September 2007, 03:01 PM
 Mumus Total Posts: 57
Re: Calculation of PPM

Unfortunately not.
I already know the number o defects which is 900.
PPM = ?
Post Number #4
5th September 2007, 03:09 PM
 Doug Tropf Total Posts: 396
Re: Calculation of PPM

For liquids or solids the calculations are usually in terms of ppm by weight, for example concentrations in water might be 1mg/L=1ppm. In the case of a gas mixture the reference is generally ppm by volume. You need to provide more details on what you are wanting to figure.
Post Number #5
5th September 2007, 03:12 PM
 Tim Folkerts Total Posts: 972
Re: Calculation of PPM

At the most basic level, PPM is just a ratio of defects to total parts --- analogous to percent.

(defective parts/total parts) = PPM/1,000,000 = percent/100

Rearranging gives
PPM = (defective parts/total parts)*1,000,000

Just like % defective is
(defective parts/total parts)*100

For example, if you have 900 defects out of 20,000 parts that would be

PPM = (900/20,000)*1,000,000 = 45,000 PPM
% defective = (900/20,000)*100 = 4.5%

(as you can perhaps see, you can also take % defective and multiple by 10,000 to get PPM)

Tim Folkerts
 Thank You to Tim Folkerts for your informative Post and/or Attachment!
Post Number #6
5th September 2007, 03:23 PM
 wweng7 Total Posts: 62
Re: Calculation of PPM

What is a total number of produced parts in a specific period? i.e. in a year, in a month etc.
Let's say in 2006 you have produced 100.000 parts and you have 900 rejects. So 900/100000 = .009 x 1,000000 = 9000 PPM in 2006
So your PPM for a last year was 9000. This is a simplest calculation of PPM.
 Thanks to wweng7 for your informative Post and/or Attachment!
Post Number #7
19th January 2010, 06:43 PM
 rmundroff Total Posts: 10
Re: Formula for the Calculation of PPM (Parts Per Million)

I understand PPM
my question from a customer's stand point
=============
if I get 100 parts in and sort them and there are 15 bad, 85 good. Do i count it as 100 Non - conforming or 15.

Does the above differ if i can sort on line w/ out slowing line down (i.e. look for missing red handle on parts)?
or If my people have to take all parts off line and measure with pair of calipers? or if I have to hire a 3rd party (which i am going to bill the supplier) to sort through parts.

what if supplier (or supplier hired 3rd party) comes in and sorts all parts in my factory
All suspect parts are counted or just the bad ones they find?

==================
Get 100 parts in
5 have Defect A wrong on them
7 have Defect B
8 have defect A & B
20 defective or 27 defective (12 w/ defect A + 15 with defect B)
==============================

What is everyone's expectations &/or history with these issues?
Post Number #8
19th January 2010, 07:01 PM
 bobdoering Total Posts: 4,036
Re: Formula for the Calculation of PPM (Parts Per Million)

The correct answer: it depends. Some customers will correct the record to actual bad parts. Other customers will not, since they figure that dealing with all 100 parts as a suspect lot is what they want to document. Some are just too "busy" (I didn't say lazy) to bother to update the records to 15. You can appeal, but it is their call.

It's pretty rare that they would count the individual defects within a part as individual counts in PPM, since its parts per million, not defects per million parts. That said, I wouldn't put it past somebody to do it, anyway.

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